Add custom 'exit' function to return from REPL.

- This doesn't doesn't terminate sys.stdin when `exit` is called, whis is important for `embed()`.
- Don't require 'exit' to be called with parentheses.

ptpython/repl.py

@@ -20,7 +20,7 @@
 import warnings
 from dis import COMPILER_FLAG_NAMES
 from pathlib import Path
-from typing import Any, Callable, ContextManager, Iterable, Sequence
+from typing import Any, Callable, ContextManager, Iterable, NoReturn, Sequence
 
 from prompt_toolkit.formatted_text import OneStyleAndTextTuple
 from prompt_toolkit.patch_stdout import patch_stdout as patch_stdout_context
@@ -40,7 +40,15 @@
 except ImportError:
  PyCF_ALLOW_TOP_LEVEL_AWAIT = 0
 
-__all__ = ["PythonRepl", "enable_deprecation_warnings", "run_config", "embed"]
+
+__all__ = [
+ "PythonRepl",
+ "enable_deprecation_warnings",
+ "run_config",
+ "embed",
+ "exit",
+ "ReplExit",
+]
 
 
 def _get_coroutine_flag() -> int | None:
@@ -91,9 +99,16 @@ def run_and_show_expression(self, expression: str) -> None:
  raise
  except SystemExit:
  raise
+ except ReplExit:
+ raise
  except BaseException as e:
  self._handle_exception(e)
  else:
+ if isinstance(result, exit):
+ # When `exit` is evaluated without parentheses.
+ # Automatically trigger the `ReplExit` exception.
+ raise ReplExit
+
  # Print.
  if result is not None:
  self._show_result(result)
@@ -155,7 +170,10 @@ def run(self) -> None:
  continue
 
  # Run it; display the result (or errors if applicable).
- self.run_and_show_expression(text)
+ try:
+ self.run_and_show_expression(text)
+ except ReplExit:
+ return
  finally:
  if self.terminal_title:
  clear_title()
@@ -383,6 +401,7 @@ def get_ptpython() -> PythonInput:
  return self
 
  globals["get_ptpython"] = get_ptpython
+ globals["exit"] = exit()
 
  def _remove_from_namespace(self) -> None:
  """
@@ -459,6 +478,29 @@ def enter_to_continue() -> None:
  enter_to_continue()
 
 
+class exit:
+ """
+ Exit the ptpython REPL.
+ """
+
+ # This custom exit function ensures that the `embed` function returns from
+ # where we are embedded, and Python doesn't close `sys.stdin` like
+ # the default `exit` from `_sitebuiltins.Quitter` does.
+
+ def __call__(self) -> NoReturn:
+ raise ReplExit
+
+ def __repr__(self) -> str:
+ # (Same message as the built-in Python REPL.)
+ return "Use exit() or Ctrl-D (i.e. EOF) to exit"
+
+
+class ReplExit(Exception):
+ """
+ Exception raised by ptpython's exit function.
+ """
+
+
 def embed(
  globals: dict[str, Any] | None = None,
  locals: dict[str, Any] | None = None,